Although the Diels-Alder condensation of dienes with an alkene to form a 6-membered ring compound is well known, and the phosphorous pentoxide dehydration of .beta.-hydroxy alkenes, .beta.-hydroxycarboxylic esters and similar compounds which upon dehydration form conjugated unsaturated systems is equally well known, the concurrent in situ reaction has not been a straight forward reaction. When the starting materials consist of the DABCO catalyzed addition product of acetaldehyde with methyl acrylate and methyl acrylate previous attempts at forming a cyclic diester condensation product have failed. The addition of acetaldehyde to ethyl acrylate in the presence of DABCO, diazabicyclo [2.2.2]-octane, has been shown, U.S. Pat. No. 3,743,669, to yield ethyl .alpha.-(1-hydroxyethyl) acrylate. The further reaction of the addition product with a second mole of the acrylate ester to form the 1,5-carboethoxy-1-cyclohexene and 1,4-carboethoxy-1-cyclohexene has not been successful heretofore. The dehydration of lower alkyl .alpha.-(1-hydroxyethyl)acrylates by phosphorous pentoxide forms an intractable polymeric product. Attempts to cause a concurrent dehydration-addition by carrying out the dehydration in the presence of a stoichiometric amount of ethyl acrylate were also unsuccessful.